Field of the Invention
The present invention relates to an apparatus and a method for configuring a sensor that detects an object based on a reflected wave from the object.
Description of the Related Art
An ultrasonic sensor composed from an ultrasonic transmitter for outputting an ultrasonic wave from an ultrasonic oscillator and an ultrasonic receiver for detecting a reflected wave from an object is known. The ultrasonic sensor can detect the object in accordance with the detection of the reflected wave and measure a distance to the object from a detection time therefor. In contrast an ultrasonic oscillator has a characteristic of outputting reverberation waves for a short period while attenuating, even if an oscillation operation has stopped.
While there are direct waves comprised from reverberation waves and transmitted waves (also referred to as oscillation waves) of an ultrasonic oscillator, it is not possible to detect a reflected wave from an object because the ultrasonic receiver will receive a direct wave. In other words, even if an object is present at a short distance, it is not possible to distinguish whether the ultrasonic receiver is directly receiving a reverberation wave or whether it is receiving a reflected wave of the object that is present at a short distance.
Japanese Patent Laid-Open No. H6-76199 recites providing a short distance determination mode that makes an interval at which an ultrasonic wave is oscillated smaller for detecting an object that is positioned at a short distance.
However, in Japanese Patent Laid-Open No. H6-76199, in a case of detecting an object by the short distance determination mode, fixing is made to the short distance determination mode and during an interval therefor it becomes impossible to detect an object present at a long distance. For example, in the case of an ultrasonic sensor apparatus installed in a multifunction peripheral and having person detection as a main purpose, if hypothetically there is a fixed object proximal to the multifunction peripheral, with a configuration according to Japanese Patent Laid-Open No. H6-76199, it becomes impossible to detect a person who is positioned further than the fixed object.